Non-Invasive Cerebellar Stimulation in Hereditary Cerebellar Ataxias

Abstract

Hereditary cerebellar ataxias (HCA) are a heterogeneous group of neurological disorders with several underlying genetic mechanisms. The available treatments are still scarce, however the growing interest in cerebellar neurostimulation has revealed promising results. We aimed to review the published studies on transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) in HCA. A literature search was performed on PubMed using the keywords: [“cerebellar stimulation” OR “transcranial direct current stimulation” OR “transcranial magnetic stimulation”] AND [“spinocerebellar ataxia” OR “hereditary ataxia” OR “Friedreich ataxia” OR “Machado Joseph disease”]. The selection was made by reading the title and abstract, followed by full article analyses. A database was created with relevant information of each article, including elements related to the study design, stimulation protocol, clinical and genetic data, clinical scales used, and neurophysiological parameters. In the initial search, 72 articles were identified, from which 25 were excluded. Despite the inclusion of ACH in various studies, some studies exhibited high genetic heterogeneity and the inclusion of acquired ataxias. Most treatment protocols consisted of stimulation sessions conducted over consecutive days, with repeat sessions scheduled after a specific period. In both techniques no significant adverse effects were recorded, and in most cases the motor benefit was evident, particularly in terms of trunk and gait ataxia. There was a longer duration of stimulation effect in tDCS when compared to TMS. The results are encouraging, regarding both the safety of stimulation and improvement in motor symptoms, in particular axial ataxia. Carrying out more studies, in genetically homogeneous population, will contribute defining the role of neuromodulation techniques in the treatment of ACH.